1. Field of the invention
The present invention relates to a lane moving-out prevention system and method in which a vehicle is prevented from moving out of a lane by controlling assist force of a power steering mechanism.
2. Prior Arts
There is an idea of realizing safety of a vehicle by positively assisting a driver's operation and a system introducing this idea is so-called Active Drive Assist (ADA) System. A primary function of the ADA system is to estimate a hazard of a collision with a forward vehicle, a hazard of a contact with an object, a possibility of a moving-out from a lane of a road and the like, based on surrounding information or running conditions of a vehicle and to inform a driver of these hazardous possibilities or to activate various control devices.
Many traffic accidents in highways are caused by drivers' inadvertent behaviors such as moving-out from a lane due to sudden drowsiness falling upon drivers. Various technologies have been developed in order to prevent the moving-out from a lane.
One of such ADA systems is exemplified by Japanese Patent Application Laid-open No. Toku-Kai-Hei 6-255514. In this ADA system, a function generator called "stable running potential energy" is established such that the stable running potential energy becomes high as the vehicle comes closer to the lane marker and it becomes low as the vehicle goes farther from the lane marker. When the stable running potential energy becomes high, an assist force of a power steering is reduced and when the stable running potential energy becomes low, the assist force is increased.
However, according to the ADA system, since the steering operation is controlled after the vehicle actually comes close to the lane marker, the responsiveness of the steering operation is insufficient. In particular, when the steering wheel is turned sharply, the system does not work properly.